Transpiration | Biology for GCSE/IGCSE - Year 11 PDF Download

Transpiration

• Water ascends through the xylem from the roots to the leaves, replenishing lost water due to transpiration.
• Transpiration occurs when water vapor escapes from the surfaces of mesophyll cells in plant leaves, followed by diffusion through the stomata.
• The xylem exhibits several adaptations:
  • Lignin deposition in cell walls leads to cell death, resulting in hollow, interconnected cells.
  • These cells form a continuous tube, facilitating the movement of water and mineral ions.
  • Lignin enhances plant strength, aiding in the resistance to water pressure.
• Xylem transport occurs unidirectionally, solely from roots to leaves, contrasting with the bidirectional movement in phloem.

Functions of Transpiration in Plants

Transpiration serves various essential functions in plants:

• It aids in the transportation of mineral ions.
• It provides water to maintain cell turgidity, supporting the plant's structure.
• Water is supplied to leaf cells for photosynthesis.
• Maintaining leaf temperature (the transformation of liquid water into water vapor as it exits cells and enters the air spaces demands heat energy. The consumption of heat during water vaporization aids in cooling the plant).